Process for the recovery of unfermented and unfermentable sugars from saccharified starch solutions



I purification of the PROCESS FOR THE RECOVERY OF UNFER;

MENTED AND FROM SACCHARIFIED TIONS UNFERMENTABLE SUGARS STARCH SOLU- Eduard Farber, New-Haven, Conn., and James S.

Wallerstein, New York, N. Y., assignors to The Overly Biochemical Research Foundation, Inc.,

New York, N. Y., a corporation of New York No Drawing. Application July 30, 1943, Serial No. 496,834

16 Claims. 1

charified starchy materials prior to subjecting such materials to a fermentation during which the separated sugars are either not converted or are converted only partially, whereby a fermerited mash is obtained, in which the content of unfermented sugar is greatly reduced over prior procedures, so that the recovery of the conversionproducts, and particularly of glycerol, i greatly facilitated.

It is a further object of the invention to effect fermented liquor obtained by the alkaline fermentation of saccharified starchy materials, by removal of a large part, if not all, of the unfermented sugar content of the liquor, so as thereby to facilitate and improve the recovery of the products of the fermentation from the liquor.

Other objects and advantages of the invention will become clear as the more detailed description thereof proceeds, and the features of novelty will be set forth in the appended claims.

In accordance with the present invention, a saccharified starchy material is subjected, either before or after fermentation, to the action of an oxide or hydroxide of an alkaline earth metal, and especially of calcium or strontium, whereby maltose and other polyoses are precipitated in the form of their more or less insoluble combinations with the alkaline earth metal oxide or hydroxide; whereafter the precipitated material may be decomposed by means of an acid, preferably one which forms an insoluble or sparingly soluble compound with the alkaline earth metal, and the maltose and other polyoses so liberated may then be acid-hydrolyzed to convert them to glucose or other fermentable sugars. This hydrolyzed sugar solution may then be combined With/8. new batch of saccharified starchy material and subjected to fermentation. Where the treatment with the alkaline earth metal oxide pound with acids 2 or hydroxide is conducted after the fermentation of the saccharified starchy material, the fermerited liquor is preferably first filtered to remove the yeast which may then be re-used for fermenting other batches.

We have found that when an alkaline earth" oxide, for example, calcium or strontium oxide, in finely ground form, is added to solutions containing maltose and other polyoses at relatively low temperatures (0 to 40 C.) a precipitate is formed which contains the polyoses in combination with the alkaline earth oxide. The precipitate settles out after a period of standing, and may be readily removed from the mother liquor by filtration, centrifugation, or often by simple decantation, preferably at low temperatures. The temperature is not critical within the specified limits; near the lower limit, formation of the compound may be slow and filtration difficult; near the upper limit, it is necessary to carry out the precipitation quickly, otherwise dark colored decomposition products are formed. These occur if the temperature is permitted to rise substantially beyond the upper limit cited.

The alkaline earth must be thoroughly admixed with the solution for a complete reaction. An efiicient way of-carrying this out consists in treating the mixture in a ball mill or similar mechanical mixing device. Subsequently, the maltose and other polyoses may be recovered from the precipitate by treatment of the comwhich form insoluble or sparingly soluble salts with. the alkaline earth metals, the effect here being to convert the alkaline earth oxides into salts and to bring the polyoses into solution. It is particularly advantageous to form a salt which is but sparingly soluble in order that the solution of the polyoses may be reasonably pure for subsequent uses. Thus, for example, maltose may be precipitated with lime and then redissolved by means of sulfuric acid, forming the sparingly soluble calcium sulfate, and leaving a fairly pure sugar solution. Gaseous acid anhydrides which form insoluble or sparingly soluble alkaline earth metal compounds, are also effective agents; thus carbon dioxide may be added down to pH 6.0, the insoluble carbonates thus formed being readily removed. Sulphur dioxide may be similarly} employed.

The process is of particular advantage where the saccharified solution of starchy materials is employed for the production of glycerol by an alkaline fermentation. Under these conditions, the glucose is fermented whereas the maltose ferments at best very slowly. Any residual un- 2,413,698 3 4 fermented sugar (consisting mainly of maltose) tion with reference to the unfermentable sugars remaining in the mash will tend to interfere present. The materials are mixed in a ball mill, with the subsequent distillation of the glycerol and the mixture permitted to stand at room temfrom the concentrated slops. Unfermented sugperature of about 25 C. A yellowish brown prears under these conditions tend to form dark 5 cipitate is formed containing disaccharides and colored and caramel-like compounds which enpolysaccharides not converted to glucose, in comtrap the glycerol formed by the fermentation and bin-ation with the lime. For complete precipitaprevent its ready volatilization by means of tion, the solution is cooled to about 5 C. oversteam. By the use of lime or other alkaline night. This precipitate is removed by filtration.

fermentable under alkaline conditions into intaken place. soluble compounds with alkaline earth oxide oi Meanwhile, the sugar-lime recipitate formed hydroxides is treated with dilute sulfuric acid the insoluble The recovered maltose may be used as such or calcium sulfate formed filtered on, the sugar be for alcoholic fermentation under non-alkaline 2n ing thereby red s l e d e acidity is amid ta mineral acid like sulfuric, and then fermented eral hours at temperatures near the iling p to glycerol under alkaline conditions. the disaccharides and polysaccharides will be By th removal of th unfermented ia converted substantially to glucose which, if depolysaccharides, either before or after an alkasired after partial or complete neutralization,

line glycerol fermentation, lighter colored slops may be added toasubsequent mash.

are obtained, improved yields of glycerol are se- Eiwmllle t e d o a a n yc After the addition of the alkaline earth metal lyzed as in Example 1. The solution remaining oxid in the specified amo nt, the mi tur will after removing the strontium oxide-unfermented show a high alkalinity. Byv reducing hi lk sugar compound from the fermented mash is contially above pH 8.0, but still in the alkaline range, acid to a pH value of about 4 and steam-distilled a considerable increase in insoluble carbohydrate under ed d p r by the lycerol is compound is obtained. This may be due to the more readily recovered than without the previous mutual influences on solubility of excess alkaremoval of the unfermented sugar, line earth metal oxides and dissolved polymeric x m 3-A slakedlime slurry is added to the carbohydrate. fermented mash of 9. glycerol fermentation. The This adjustment of the pH can be carried out solution contains 2% alcohol and about 4% unby using carbon dioxide gas in such amounts'that ferm nted car ohydrate sugars as well as 3% the alkalinity is lowered to a pH range between glycerine. 40 grams of the slaked lime per liter 7.5 and 8.0. are added slowly with stirring at a temperature This additional re oval of carbohydrate from of 25 C. When the stirring is discontinued after glycerine is to be recovered. A further advanadded to the solution with stirring, and the pH is tage achieved by this method in the case of ferthereby reduced from about 11 5 to 8 0. The solumentation mashes consists in producing solutions tion ls then filtered and about of the unferwhich on concentrating remain clear and do not merited carbohydrate is removed from the soludeposit large amounts of insoluble matter tion The precipitate is acid hydrolyzed with sul- In recovering sugar from a fermented mash by 60 furic acid at pH 0 to 1 and added to a subsevantageous to precipitate the unfermented sugar The fermented mash from which the precipitate prior to recovery of the alcohol contained in the is removed i concentrated and subjected to a fermentation liquor. steam distillation for the recovery of glycerol Example 1.A wheat mash is used for the pro- The mash to be fermented may be obtained by means of dilute mineral acids, as, for example, We claimsulfuiic acid Subsequently the acidity is neu- 1. The method of'separatin maltose from solutralized b means of lime, forming calcium sultions of saccharified starchy materials containing fate, which is separated. Thereafter finely the same, compiising adding to such a solution 5 metal oxides and hydroxides at temperatures of earth metal oxides about -40 C. and in quantity sufficient to precipitate at least a substantial part of the maltose, mixing the materials and allowing them to stand until the compound of the metal base with the maltose begins to settle, removing the insoluble compound from the solution, and decomposing the compound by means of a member of the group consisting of acids and acid anhydrides which form sparingly soluble salts with the alkaline earth metal.

2. The method according to claim 1, in which the pH after precipitating the compound of maltose with the alkaline earth base is adjusted to between about 7.5 and 8.0 before separating the insoluble compound from the solution. 7

3. The method according toclaim 1, wherein after the precipitation of the compound of the alkaline earth metal base and the maltose the pH value is adjusted to between about 7.5 and 8.0 with carbon dioxide gas before separating the insoluble compound from the solutio 4. The method according to clalm 1, in which the precipitation of the maltose is carried out in the'presence of alcohol.

5. The method of separating maltose from solutions of saccharified starchy materials containing the same, comprising adding to such a solution a member of the group consisting of alkaline and hydroxides in quantity sufficient to precipitate at least a substantial part of the maltose, intimately mixing the materials to promote reaction, separating the sugar precipitate from the solution, and subsequently decomposing the precipitate to liberate the soluble sugars.

6. Method according to claim 5, wherein the decomposition is effected with the aid of a member of the group consisting of acids and acidanhydrides which form sparingly soluble salts with the alkaline earth metal.

'7. Method according to claim 5, wherein the alkaline earth metal compound is calcium oxide.

8. Method according to claim 5, wherein the alkaline earth metal compound is strontium oxide.

9. Method according to claim 5, wherein the alkaline earth metal compound is calcium hydroxide.

10. Method according to claim 5, wherein the decomposition of the precipitate is effected with dilute sulfuric acid.

11. The method of separating maltose from solutions of saccharifled starchy materials contain-l ing the same, comprising fermenting a solution of saccharified starchy material for the production of glycerol, adding to the fermented solution a member of the group consisting of alkaline earth metal oxides and hydroxides at a temperature no 1 higher than about 40 C. and in quantity sufficient to precipitate at least a substantial part of the maltose, mixing the materials and allowing them to stand until the compound of the metal base with the maltose begins to settle, removing the insoluble compound from the solution, and decomposing the compound by means of a member of the group consisting of acids and acid anhydrides which form sparingly soluble salts with the alkaline earth metal.

12. Process according to claim 11, wherein the adding of the alkaline earth metal base is made in the presence of the alcohol formed during the fermentation.

13. The method for the manufacture of glycerol which comprises adding to a, maltose-containing solution of saccharified starchy materials a member of the group consisting of alkaline earth metal oxides and hydroxides at temperatures no higher than about 40 C. and in quantity sufficient to precipitate at least a substantial part of the maltose, separating the precipitate of the metal base with the maltose, subjecting the residual sugar solution to fermentation under alkaline conditions, and subsequently distilling glycerol from the fermented solution.

14. The method for the manufacture of glycerol which comprises fermenting a solution of saccharlfied starchy material under alkaline conditions and, prior to distillation of the formed glycerol, treating the solution with a metal base of the group consisting of alkaline earth metal oxides and hydroxides at a temperature no higher than about 40 C. and in quantity sufficient to precipitate at least a substantia1 part of the maltose, and separating the precipitate of the metal base with the maltose.

15. The method according to claim 14, wherein the treatment with the alkaline earth metal base takes place after the fermentation and in the presence of the formed alcohol.

16. The method according to claim 14, wherein the treatment with the alkaline earth metal base takes place at approximately room temperature.

EDUARD BARBER. JAMES s. WALLERSTEIN. 

